Not really, says Stefan Bright, the safety director for the International Window Cleaning Association. "It's pretty rare that anybody gets killed in one of these permanent platforms," Bright says. The full technical name of the type of platform that failed on the Hearst Tower is a "permanently installed powered platform," and of the 500 to 700 of them currently in use across the United States, a whopping 70 to 80 percent of them are in New York City. They're typically designed for buildings over 300 feet.

Back in February,The New Yorker published a lengthy article on window-washers (which these two workers yesterday were not, although they were on a window-washing apparatus), noting that "the work of washing windows in the United States is significantly safer than driving a cab." Bright says that in fact there was one fatality in the entire national window-washing industry last year, and two the year before that. U.S. Bureau of Labor Statistics data from 2010, the most recent year with clear definitions on these categories, confirm that fatality rates due to falls for window-washers, janitors, and cleaners are indeed quite low.

The specific platform on the Hearst Tower is a little tricky, as it's designed to bend around the peculiar angles of the building. The same New Yorker piece highlighted this $3-million system on the Hearst Tower, installed in 2005, and designed and built by Toronto-based Tractel-Swingstage:

Designing and building the machine took a team of Tractel engineers three years. The result, a rectangular steel box the size of a Smart car, supporting a forty-foot mast and a hydraulic boom arm attached by six strands of wire rope to a telescopic cleaning basket, houses a computer that monitors sixty-seven electromechanical safety sensors and switches, and runs around the roof of the Hearst Tower on four hundred and twenty feet of elevated steel track.

"The platform itself is designed to fold into 90 degrees so it can wrap around the corners," Bright says. The workers on the platform yesterday were maintenance workers, he explained, who were there to fix an earlier problem identified with the platform not straightening. While he isn't clear on the sequence of events between the problem being discovered and the maintenance workers getting struck on the platform, it appeared the raising and lowering element stopped working. There are also reports that a motor failed in the device. The state's Department of Labor and New York City's Department of Buildings will be investigating yesterday's failure.

But these devices just get stuck every once in a while, according to Bright. He pointed out an incident in May, when two window-washers in San Diego were stranded on a building for over an hour before being rescued.

News outlets are also drawing links to another incident in New York City back in 2007, when two window washers fell 47 stories after the scaffolding collapsed. Miraculously, one of the men survived. NBC New York reports that the same company that designed the Hearst Tower's device, Tractel, helped maintain the Upper East Side window washing scaffold that fell in 2007. The U.S. Occupational Safety and Health Administration issued Tractel three citations following that incident.